The Test-Node stage-and-swap relies on Rename-Item's same-directory
carve-out: -NewName accepts a path only when it shares the directory of
-Path (FileSystemProvider strips the directory and keeps the leaf), and
all four swap calls rename between $HermesHome\node and sibling
node.new-* / node.old-* paths. Pin that invariant so a future refactor
cannot introduce a cross-directory rename, which would throw on every
Windows install and read as a false "in use" deferral.
Source-level probe, matching the other tests/test_install_ps1_*.py
regressions (Linux CI cannot execute the Windows installer).
David Metcalfe